Adhesive film and pouch-type secondary battery including the same

Abstract

The present invention relates to an adhesive film including: an outer insulating layer; and a pressure-sensitive adhesive layer provided on one surface of the outer insulating layer, wherein the pressure-sensitive adhesive layer includes a thermosetting resin, the adhesive film satisfies at least one of an adhesion to a stainless steel substrate of greater than or equal to 100 gf / 25 mm and an adhesion to a polyester resin substrate of greater than or equal to 200 gf / 25 mm, and the adhesion is measured by pressing a surface of the pressure-sensitive adhesive layer opposite to the surface in contact with the outer insulating layer onto the stainless steel substrate or the polyester resin substrate using a roll of 2 kg, and then peeling the adhesive film at a peeling speed of 300 mm / min and a peeling angle of 180° at 140°C.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0068918, filed on May 27, 2024, the disclosure of which is incorporated herein by reference. Technical Field

[0004] The present invention relates to an adhesive film and a pouch-type secondary battery including the adhesive film, and more particularly, to an adhesive film that ensures heat resistance during the folding process of the battery case of the pouch-type secondary battery and a pouch-type secondary battery including the adhesive film. Background Technology

[0005] Recently, with the rapid expansion of electric vehicle (EV) adoption, the demand for high-energy-density lithium-ion batteries is increasing. Therefore, pouch-type battery boxes that optimize space utilization and reduce weight are being actively developed.

[0006] Pouch-type battery cases are fabricated by forming a cup-shaped portion in a flexible pouch film using compression molding, housing electrode assemblies within the cup-shaped portion, and then sealing the periphery of the cup-shaped portion. However, because the sealing portion—which is the periphery of the sealed cup-shaped portion—may protrude more than the rest of the case, the energy density may be reduced, and there may be problems with deteriorated insulation performance due to weakened seals at the ends of the sealing portion or exposure of the metal barrier layer in the pouch film. To address this issue, a method of folding the sealing portion is used.

[0007] Methods for folding the sealing portion include single-sided folding (SSF), where the end of the sealing portion is folded 90° toward the cup-shaped portion; wing-type folding (WF), where the end of the sealing portion is folded 180° toward the cup-shaped portion; and double-sided folding (DSF), where the end of the sealing portion is folded 270° toward the cup-shaped portion. In the past, single-sided and double-sided folding were primarily used, where the folding and protection of the end of the sealing portion are secured by using an adhesive film to surround the sealing portion and the cup-shaped portion, which are tightly attached by the above methods.

[0008] However, regarding single-sided and double-sided folding, because they may cause relatively greater damage to the sealing portion compared to wing-type folding, wing-type folding is increasingly being used as an alternative to conventional single-sided and double-sided folding. However, unlike single-sided and double-sided folding, wing-type folding does not allow for secure fixation with adhesive film after folding because one surface of the sealing portion is not tightly attached to the cup-shaped portion. Therefore, for wing-type folding, the following method is used: before folding, adhesive film is attached to the end of the sealing portion, then the end of the sealing portion is folded 180°, and heat is applied to the corresponding portion to fix the folded portion.

[0009] However, regarding conventional single-sided and double-sided folding, since there is no need to apply heat to the adhesive film during the fixing period, the adhesive film used in conventional single-sided and double-sided folding has low durability at high temperatures, and therefore it is difficult to use the adhesive film directly in the wing folding method. Summary of the Invention Technical issues

[0010] One aspect of the present invention aims to provide an adhesive film that does not separate due to its excellent heat resistance in high-temperature environments and a pouch-type secondary battery including the adhesive film. Technical solution

[0011] [1] The present invention provides an adhesive film comprising: an outer insulating layer; and an adhesive layer disposed on a surface of the outer insulating layer, wherein the adhesive layer comprises a thermosetting resin, and the adhesive film satisfies at least one of an adhesion force to a stainless steel substrate of greater than or equal to 100 gf / 25 mm and an adhesion force to a polyester resin substrate of greater than or equal to 200 gf / 25 mm, wherein the adhesion force is the adhesion force when the adhesive film is peeled off at 140°C at a peeling speed of 300 mm / min and a peeling angle of 180° after pressing the surface of the adhesive layer opposite to the surface in contact with the outer insulating layer onto the stainless steel substrate or the polyester resin substrate using a 2 kg roller.

[0012] [2] The present invention provides the adhesive film of [1] above, wherein the stainless steel substrate is a SUS304 substrate.

[0013] [3] The present invention provides the adhesive film of [1] or [2] above, wherein the thermosetting resin is a silicone resin, an epoxy resin, or a combination of silicone resin and epoxy resin.

[0014] [4] The present invention provides an adhesive film of at least one of [1] to [3] above, wherein the adhesive layer includes a curing agent.

[0015] [5] The present invention provides the adhesive film of [4] above, wherein the thermosetting resin is a silicone resin and the curing agent includes silane groups (Si-H groups).

[0016] [6] The present invention provides the adhesive film of [4] above, wherein the thermosetting resin is an epoxy resin and the curing agent is an amine curing agent.

[0017] [7] The present invention provides an adhesive film of at least one of [1] to [6] above, wherein the adhesive layer comprises an adhesive agent.

[0018] [8] The present invention provides the adhesive film of [7] above, wherein the tackifier includes at least one selected from rosin resin, terpene resin, hydrocarbon resin, hydrogenated hydrocarbon resin, styrene resin, phenolic resin and xylene resin.

[0019] [9] The present invention provides an adhesive film of at least one of [1] to [8] above, wherein the stainless steel substrate is a SUS304 substrate.

[0020]

[10] The present invention provides an adhesive film of at least one of [1] to [9] above, wherein the polyester resin substrate is a polyethylene terephthalate (PET) substrate.

[0021]

[11] The present invention provides an adhesive film of at least one of [1] to

[10] above, wherein the thermosetting resin is included in an amount of 10% to 99% by weight based on the total weight of the adhesive layer.

[0022]

[12] The present invention provides an adhesive film of at least one of [1] to

[11] above, wherein the adhesive film has an adhesion force of less than or equal to 500 gf / 25 mm to a stainless steel substrate and a polyester resin substrate.

[0023]

[13] The present invention provides an adhesive film of at least one of [1] to

[12] above, wherein the storage modulus (G') of the adhesive layer at 140°C is 1×10 4 Pa to 1×10 6 Within the range of Pa.

[0024]

[14] The present invention provides an adhesive film of at least one of [1] to

[13] above, wherein the loss modulus (G) of the adhesive layer at 140°C is 2 × 10⁻⁶. 3 Pa to 1×10 5 Within the range of Pa.

[0025]

[15] The present invention provides an adhesive film of at least one of [1] to

[14] above, wherein the tanδ (G” / G’) of the adhesive layer at 140°C is in the range of 0.01 to 0.45.

[0026]

[16] The present invention provides an adhesive film of at least one of [1] to

[15] above, wherein the adhesive film has a thickness of 30 μm to 150 μm.

[0027]

[17] The present invention provides a pouch-type secondary battery comprising: an electrode assembly including a positive electrode, a negative electrode and a separator; a pouch-type case including a receiving portion for receiving the electrode assembly, and a platform portion and a sealing portion formed along the periphery of the receiving portion; an electrode tab protruding from each of the positive and negative electrodes of the electrode assembly; an electrode lead connected to the electrode tab and protruding outward via the platform portion; and an adhesive film of any of [1] to

[16] above, the adhesive film being configured to surround a cross section exposed at the end of the sealing portion. Beneficial effects

[0028] The adhesive film according to the invention improves its heat resistance by including a thermosetting resin in the adhesive layer and ensuring that the adhesion force measured at high temperature (140°C) meets a specific range. Therefore, even during the manufacturing process of a lithium secondary battery, when the adhesive film on the sealing portion of the battery case is pressed at high temperature, the adhesive film will not separate from the outer surface of the battery case. In particular, when the sealing portion is folded in a wing-fold manner, the folded portion can be effectively fixed using the adhesive film according to the invention because the adhesive film will not separate even when pressed at high temperature, and advantageously, insulation performance is ensured by effectively protecting the ends of the sealing portion. Furthermore, leakage of the adhesive layer components during the high-temperature pressing process of the adhesive film and subsequent battery contamination caused by the adhesive layer components can be prevented, and the processability and appearance defects of the battery can be improved. Attached Figure Description

[0029] Figure 1 This is a cross-sectional view illustrating the lamination state of the adhesive film according to an embodiment of the present invention.

[0030] Figure 2 This is an exploded assembly diagram of a pouch-type secondary battery before it is sealed.

[0031] Figure 3 This is a cross-sectional view of a sealed pouch-type secondary battery.

[0032] Figure 4 This is a cross-sectional view of a pouch-shaped secondary battery with its sealed portion folded. Detailed Implementation

[0033] The invention will be described in more detail below.

[0034] It will be understood that the words or terms used in the specification and claims should not be interpreted as having the meaning defined in a commonly used dictionary, and it will be further understood that, based on the inventor's ability to appropriately define the meaning of words or terms in order to best illustrate the principles of the invention, the words or terms should be interpreted as having a meaning consistent with their meaning in the context of the relevant field and technical concept of the invention.

[0035] In this invention, "storage modulus (G')" refers to the amount of elastic energy stored in a material under oscillation. The storage modulus (G') was measured using a rotational rheometer (TA Instruments product name: DHR-20) in oscillation frequency scanning mode, at a frequency of 1 Hz and a frequency range of 0.1 Hz to 100 Hz, under conditions of 5% strain.

[0036] In this invention, "loss modulus (G)" refers to the amount of elastic energy lost in a material under oscillation. The loss modulus (G) was measured using a rotational rheometer (TA Instruments product name: DHR-20) in oscillation frequency sweep mode, at a frequency of 1 Hz and a frequency range of 0.1 Hz to 100 Hz, under conditions of 5% strain.

[0037] In this invention, "tanδ(G” / G')" refers to the ratio of loss modulus to energy storage modulus, and after measuring the energy storage modulus and loss modulus using the above method, it can be calculated using the formula G” / G'.

[0038] Adhesive film

[0039] The adhesive film according to the invention comprises: an outer insulating layer; and an adhesive layer disposed on one surface of the outer insulating layer. The adhesive layer comprises a thermosetting resin.

[0040] The adhesive film satisfies at least one of an adhesion force of ≥100 gf / 25 mm to a stainless steel substrate and an adhesion force of ≥200 gf / 25 mm to a polyester resin substrate, and preferably has an adhesion force of ≥100 gf / 25 mm to a stainless steel substrate and an adhesion force of ≥200 gf / 25 mm to a polyester resin substrate. When the above ranges are met, even during the folding process of the battery case in the manufacturing process of the lithium secondary battery, when the sealed portion with the adhesive film attached is pressed at high temperature, the adhesive film will not separate, and the problem of the adhesive layer components melting and leaking to the outside of the adhesive film can be prevented.

[0041] In this paper, adhesion force is the adhesion force when the adhesive layer is peeled off at 140°C, at a peeling speed of 300 mm / min and a peeling angle of 180° after pressing the surface of the adhesive layer opposite to the surface in contact with the outer insulation layer onto a stainless steel substrate or a polyester resin substrate using a 2 kg roller.

[0042] Pouch-type battery cases are fabricated by forming a cup-shaped portion in a flexible pouch film using compression molding, housing electrode assemblies within the cup-shaped portion, and then sealing the periphery of the cup-shaped portion. However, because the sealing portion—which is the periphery of the sealed cup-shaped portion—may protrude more than the rest of the case, the energy density may be reduced, and there may be problems with deteriorated insulation performance due to weakened seals at the ends of the sealing portion or exposure of the metal barrier layer in the pouch film. To address this issue, a method of folding the sealing portion is used.

[0043] Conventionally, the main methods for folding the sealing part are single-sided folding, which folds the end of the sealing part towards the cup-shaped part by 90°, and double-sided folding, which folds the end of the sealing part towards the cup-shaped part by 270°. However, due to the problem that single-sided folding and double-sided folding cause greater damage to the sealing part, wing-type folding, which folds the end of the sealing part towards the cup-shaped part by 180°, has been increasingly used recently.

[0044] However, regarding conventional single-sided and double-sided folding, since one surface of the sealing portion is tightly attached to the cup-shaped portion during folding, the folded portion can be secured and the end of the sealing portion protected by attaching an adhesive film to surround the tightly attached portion. However, regarding wing-type folding, since the sealing portion is not tightly attached to the cup-shaped portion during folding, the adhesive film cannot be used to secure the folded portion after folding. Therefore, for wing-type folding, the following method is used: before folding, the adhesive film is attached to the end of the sealing portion, then the end of the sealing portion is folded 180°, and heat is applied to the corresponding portion to secure the folded portion.

[0045] However, regarding conventional single-sided and double-sided folding, since there is no need to apply heat to the adhesive film during the fixing period, the adhesive film used in conventional single-sided and double-sided folding has low durability at high temperatures, and therefore it is difficult to use the adhesive film directly in the wing folding method. Specifically, when the adhesive film used in conventional single-sided and double-sided folding is used in wing folding, problems such as the adhesive film separating during high-temperature pressing or the components of the adhesive layer melting and leaking to the outside of the adhesive film may occur.

[0046] Therefore, as a result of extensive research into developing adhesive films with improved durability at high temperatures, the inventors of this invention discovered that by controlling the adhesive force of the adhesive layer within a specific range at high temperatures (e.g., 140°C), not only can the problem of adhesive film separation during the high-temperature pressing process after folding be prevented, but the problem of melting of the components of the adhesive layer can also be solved, thus completing this invention.

[0047] Adhesion strength can be adjusted by the type and content of the thermosetting resin, tackifier, and curing agent, the surface treatment and surface roughness of the adhesive layer, and the thickness and composition of the combined outer insulating layer. For example, when silicone resin is used as the thermosetting resin, adhesion strength can be appropriately adjusted by using PDMS (polydimethylsiloxane) with vinyl-terminated groups as the silicone resin or by using a curing agent with silanol groups (Si-H groups) for hydrogenation silanization. Furthermore, when epoxy resin is used as the thermosetting resin, adhesion strength can be appropriately adjusted by including -OH groups in the epoxy resin or by using an amine curing agent.

[0048] Specifically, the adhesive film may have an adhesion force to a stainless steel substrate of greater than or equal to 100 gf / 25 mm, greater than or equal to 102 gf / 25 mm, greater than or equal to 104 gf / 25 mm, greater than or equal to 106 gf / 25 mm, greater than or equal to 108 gf / 25 mm, or greater than or equal to 110 gf / 25 mm, and may have an adhesion force to a stainless steel substrate of less than or equal to 500 gf / 25 mm, less than or equal to 450 gf / 25 mm, less than or equal to 400 gf / 25 mm, less than or equal to 350 gf / 25 mm, less than or equal to 300 gf / 25 mm, less than or equal to 250 gf / 25 mm, less than or equal to 200 gf / 25 mm, or less than or equal to 160 gf / 25 mm, wherein the above numerical ranges may be combined without limitation. For example, the adhesive film can have an adhesion force to a stainless steel substrate of greater than or equal to 100 gf / 25 mm, 100 gf / 25 mm to 500 gf / 25 mm, 104 gf / 25 mm to 300 gf / 25 mm, or 110 gf / 25 mm to 160 gf / 25 mm. The adhesion force to the stainless steel substrate is measured when the adhesive film is peeled off at 140°C at a peel speed of 300 mm / min and a peel angle of 180° after pressing the surface of the adhesive layer opposite to the surface in contact with the outer insulating layer onto the stainless steel substrate using a 2 kg roller. If the adhesion force of the adhesive film to the stainless steel substrate is lower than the above ranges, the adhesive layer components may melt and flow out during high-temperature pressing during wing folding, and the adhesive film may separate, thus failing to secure the folded portion. Therefore, when the adhesion of the adhesive film to the stainless steel substrate meets the above range, the components of the adhesive film will not melt even when pressed at high temperatures (e.g., greater than or equal to 140°C) during wing folding, thus improving the processability and appearance defects of the battery. Furthermore, since the adhesive film will not separate from the sealed portion to which it is attached, insulation performance can be maintained while effectively fixing the folded portion and protecting the ends of the sealed portion.

[0049] The adhesive film can have an adhesion force to a polyester resin substrate of greater than or equal to 200 gf / 25 mm, greater than or equal to 202 gf / 25 mm, greater than or equal to 204 gf / 25 mm, greater than or equal to 206 gf / 25 mm, greater than or equal to 208 gf / 25 mm, or greater than or equal to 210 gf / 25 mm, and can have an adhesion force to a polyester resin substrate of less than or equal to 500 gf / 25 mm, less than or equal to 450 gf / 25 mm, less than or equal to 400 gf / 25 mm, less than or equal to 350 gf / 25 mm, less than or equal to 300 gf / 25 mm, or less than or equal to 270 gf / 25 mm. For example, the adhesive film can have an adhesion force to a polyester resin substrate of greater than or equal to 200 gf / 25 mm, 200 gf / 25 mm to 500 gf / 25 mm, 204 gf / 25 mm to 350 gf / 25 mm, or 210 gf / 25 mm to 270 gf / 25 mm. The adhesion force to the polyester resin substrate is the force when the adhesive film is peeled off at 140°C at a peel speed of 300 mm / min and a peel angle of 180° after pressing the adhesive layer onto the polyester resin substrate using a 2 kg roller. If the adhesion force of the adhesive film to the polyester resin substrate is lower than the above ranges, the adhesive layer components may melt and flow out during high-temperature pressing during wing folding, and the adhesive film may separate, thus failing to secure the folded portion. Therefore, when the adhesion of the adhesive film to the polyester resin substrate meets the above range, the components of the adhesive film will not melt even when pressed at high temperatures (e.g., greater than or equal to 140°C) during wing folding, thus improving the processability and appearance defects of the battery. Furthermore, since the adhesive film will not separate from the sealed portion to which it is attached, insulation performance can be maintained while effectively fixing the folded portion and protecting the ends of the sealed portion.

[0050] The stainless steel substrate can be a SUS304 substrate.

[0051] Polyester resin substrates can be polyethylene terephthalate (PET) substrates.

[0052] The storage modulus (G') of the adhesive layer at 140°C can reach 1×10⁻⁶. 4 Pa to 1×10 6 Pa, 1.5 × 10 4 Pa to 5×10 5 Pa, 2×10 4 Pa to 2×10 5 Pa, or 3.5 × 10 4 Pa to 7×10 4Within the range of Pa. If the above range is met, the adhesion can be excellent due to sufficient cohesion in the adhesive layer.

[0053] The loss modulus (G) of the adhesive layer at 140°C can reach 2×10 3 Pa to 1×10 5 Pa, 2.5 × 10 3 Pa to 5×10 4 Pa, 4×10 3 Pa to 3×10 4 Pa, or 8×10 3 Pa to 2×10 4 Within the range of Pa. Under the condition that the above range is met, the adhesive layer can have excellent adhesion to the adherend.

[0054] The tanδ (G” / G’) of the adhesive layer at 140°C can be in the range of 0.01 to 0.45, 0.05 to 0.40, 0.1 to 0.3, or 0.2 to 0.3. When the above ranges are met, the problem of separation during high-temperature processing can be solved because the adhesive layer has excellent adhesion.

[0055] The adhesive film can have a thickness of 20 μm to 150 μm, 30 μm to 120 μm, 35 μm to 100 μm, 40 μm to 80 μm, or 50 μm to 70 μm. By meeting these ranges, the adhesive film can possess sufficient adhesion, durability, heat resistance, and insulation properties while minimizing the space occupied by the adhesive film in the lithium secondary battery.

[0056] Figure 1 This is a cross-sectional view illustrating the laminated state of the adhesive film 10 according to an embodiment of the present invention.

[0057] Reference Figure 1 According to an embodiment of the present invention, the adhesive film 10 includes an outer insulating layer 11 and an adhesive layer 12 disposed on one surface of the outer insulating layer 11.

[0058] The form of the adhesive film 10 is not limited to vary depending on the intended use. For example, the adhesive film 10 used to fix the shape of the electrode assembly can be in the form of a rectangular flat plate, but it is not limited to this and can be used in various forms such as circular, triangular or irregular flat plates.

[0059] (1) Outer insulation layer

[0060] The outer insulating layer according to the invention provides the mechanical stiffness required to achieve the adhesion force of the adhesive film 10. It can be made of a material with insulating properties to insulate the adhesive film 10 from the outside and protects the adhesive layer from friction and impact. In this case, the outer insulating layer 11 is a layer in the form of a film or sheet, wherein, in addition to a rectangular shape, the outer insulating layer 11 can also have shapes such as circular, triangular, or irregular shapes.

[0061] The outer insulation layer 11 can be used without particular restrictions, as long as it serves to provide mechanical rigidity to the adhesive film 10 and protect the adhesive layer. For example, the outer insulation layer 11 may include at least one selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl chloride (PVC), polyimide (PI), cast polypropylene (CPP), high-density polyethylene (HDPE), and low-density polyethylene (LDPE).

[0062] Preferably, the outer insulating layer 11 may include at least one selected from polyethylene terephthalate and polyimide, and more preferably polyimide. In this case, when the outer insulating layer 11 is combined with the adhesive layer according to the invention, the adhesion to stainless steel substrates and the adhesion to polyester resin substrates can be further improved, thereby improving the heat resistance of the adhesive film.

[0063] The thickness of the outer insulating layer 11 can be in the range of 10 μm to 60 μm, 15 μm to 50 μm, 20 μm to 45 μm, or 20 μm to 30 μm. When the thickness of the outer insulating layer 11 meets the above range, the adhesion of the adhesive film 10 can be improved, and since the tensile strength of the outer insulating layer 11 is sufficiently ensured, the tape is not easy to break during the winding process of attaching the adhesive film 10 to the secondary battery, and the attachment process can be easy.

[0064] (2) Adhesive layer

[0065] According to the present invention, the adhesive layer 12 can serve to attach the adhesive film 10 to the object to be bonded, and specifically, it can serve to attach the adhesive film 10 to the sealing portion of the battery box included in the lithium secondary battery by contacting the outer surface of the sealing portion.

[0066] The adhesive layer 12 comprises a thermosetting resin.

[0067] Thermosetting resin refers to a resin that cures upon heating. During the folding process of the sealing portion after sealing the battery box, when heat is applied at high temperatures while pressing, the thermosetting resin can prevent the adhesive film from separating during high-temperature pressing by improving the heat resistance of the adhesive film 10. Specifically, during the preparation of lithium secondary batteries, in order to prevent the adhesive film from separating during the process of attaching the adhesive film to the portion without electrode leads at the end of the sealing portion, folding the sealing portion, and then pressing the sealing portion with the attached adhesive film at high temperatures, it is important to maintain the heat resistance at a certain level or higher. Therefore, since the adhesive film according to the present invention can enhance the heat resistance of the adhesive layer by including a thermosetting resin in the adhesive layer, a certain level or higher adhesion force of the adhesive layer can be achieved even at high temperatures, and thus separation of the adhesive film during the high-temperature pressing process can be prevented.

[0068] The thermosetting resin can be silicone resin, epoxy resin, or a combination of silicone resin and epoxy resin. In this case, since the structural stability of the thermosetting resin is excellent even when heated at high temperatures for extended periods, the adhesive layer can have sufficient heat resistance even when pressed at high temperatures (e.g., 140°C). Therefore, the problem of adhesive film 10 separation during the wing-folding process can be prevented, and the problem of component leakage of the adhesive layer can be prevented. Specifically, when the thermosetting resin is silicone resin, the adhesion can be adequately maintained even at high temperatures because silicone resin has high heat resistance and electrical insulation properties. Furthermore, when the thermosetting resin is epoxy resin, the resin has excellent durability and impact resistance, and can have high strength due to polymer crosslinking when exposed to heat. Therefore, it has excellent stability even at high temperatures, and the adhesion can be adequately maintained even at high temperatures.

[0069] Silicone resin refers to a resin having a backbone comprising bonds formed by alternating bonding of silicon with organic groups and oxygen. Silicone resin may include at least one selected from polydimethylsiloxane (PDMS), polydiphenylsiloxane, and polyfluorosiloxane, and may preferably include polydimethylsiloxane. In this case, the heat resistance of the adhesive film can be improved because adhesion to polyester resin substrates and adhesion to stainless steel substrates can be further enhanced.

[0070] Furthermore, the silicone resin may include vinyl end groups. In this case, since the adhesion strength of the adhesive layer at high temperatures can be adjusted to the desired range, problems with adhesive film separation during the pressing process after folding can be prevented.

[0071] Epoxy resin can refer to a resin whose molecule contains two or more epoxy bonds. For example, epoxy resin may include at least one selected from cresol-formaldehyde epoxy resin, bisphenol F type epoxy resin, bisphenol F type phenolic epoxy resin, bisphenol A type epoxy resin, bisphenol A type phenolic epoxy resin, phenolic epoxy resin, tetrafunctional epoxy resin, biphenyl type epoxy resin, biphenyl type phenolic epoxy resin, pyrrolidone type epoxy resin, alkyl-modified pyrrolidone type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, dicyclopentadiene-modified phenol type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, and aliphatic cyclic epoxy resin. In this case, the heat resistance of the adhesive film can be improved because the adhesion to polyester resin substrates and the adhesion to stainless steel substrates can be further improved.

[0072] Furthermore, epoxy resins may include hydroxyl groups (OH groups). In this case, since the adhesion strength of the adhesive layer at high temperatures can be adjusted to the desired range, problems such as insulation degradation and adhesive film separation during the pressing process after folding can be prevented.

[0073] Thermosetting resins can have a weight-average molecular weight of 10,000 g / mol to 1,000,000 g / mol, 30,000 g / mol to 700,000 g / mol, or 40,000 g / mol to 600,000 g / mol. Excellent durability of the adhesive layer can be achieved when these ranges are met.

[0074] Based on the total weight of the adhesive layer 12, the thermosetting resin may be included in an amount ranging from 10% to 99% by weight. Specifically, based on the total weight of the adhesive layer 12, the thermosetting resin may be included in an amount greater than or equal to 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80% by weight, and may also be included in an amount less than or equal to 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, or 60% by weight. These ranges can be combined without limitation. For example, based on the total weight of the adhesive layer 12, the thermosetting resin may be included in an amount ranging from 10% to 99%, 50% to 90%, or 60% to 90% by weight. If the above conditions are met, the excellent durability and heat resistance of the adhesive layer can be ensured.

[0075] The adhesive layer may include a curing agent. The curing agent can chemically crosslink the thermosetting resin to improve the cohesiveness of the adhesive layer and improve its adhesion at high temperatures.

[0076] When the thermosetting resin is a silicone resin, the curing agent can be a curing agent including silane-hydrogen groups (Si-H groups), and specifically may contain a dimethylsiloxane-methylhydrosiloxane copolymer. In this case, the adhesion can be appropriately adjusted by the hydrogenation and silylation of the silicone resin and the curing agent.

[0077] Furthermore, when epoxy resin is used as a thermosetting resin, the curing agent can be an amine curing agent, and specifically an imidazole curing agent. In this case, the cohesive force of the adhesive layer can be enhanced by fully performing a curing reaction with the epoxy resin, and the adhesion force can be appropriately adjusted.

[0078] Based on the total weight of the adhesive layer, the curing agent may be included in an amount of 0.1% to 30%, 0.5% to 20%, or 1% to 10% by weight. When these ranges are met, the adhesion strength can be improved to the desired range by appropriately providing adhesive properties and cohesion to the adhesive layer.

[0079] Thermosetting resins and curing agents can be included in weight ratios of 50:50 to 99.3:0.7, 70:30 to 99:1, 90:10 to 98.7:1.3, or 95:5 to 98.5:1.5. When these ranges are met, excellent adhesion can be achieved at high temperatures due to the full cross-linking of the thermosetting resin and curing agent.

[0080] Based on the crosslinkable functional groups, the thermosetting resin and the curing agent can be included in a weight ratio of 0.1:1 to 5:1, 0.5:1 to 2:1, or 0.8:1 to 1.5:1. When these ranges are met, the thermosetting resin and the curing agent can react to increase the crosslinking density, and therefore, the adhesion can be excellent.

[0081] The adhesive layer may include a tackifier. The tackifier can improve the adhesion of the surface of the adhesive layer 12 to the substrate.

[0082] When the adhesive layer consists only of thermosetting resin, the initial tack of the adhesive film may be insufficient. Therefore, when the adhesive layer also includes a tackifier, sufficient initial tack can be ensured, and thus the initial adhesion performance can be excellent. Furthermore, the separation of the adhesive film can be further prevented not only at high temperatures but also at room temperature.

[0083] The tackifier may include at least one selected from rosin-based resins, terpene-based resins, hydrocarbon resins, hydrogenated hydrocarbon resins, styrene-based resins, phenolic resins, and xylene-based resins, and may preferably include at least one selected from hydrogenated hydrocarbon resins and rosin-based resins. For example, when the thermosetting resin is silicone resin, the tackifier may include hydrogenated hydrocarbon resins, and when the thermosetting resin is epoxy resin, the tackifier may include rosin-based resins. In this case, the adhesion of the adhesive layer can be sufficiently enhanced, so that the adhesive film 10 can be firmly adhered to the outer surface of the battery case.

[0084] Specifically, rosin resins can be a concept encompassing both rosin and rosin derivative resins. For example, rosin includes: unmodified rosin (raw rosin), such as resin rosin, tall oil rosin, and wood rosin; modified rosin, such as hydrogenated rosin, disproportionated rosin, and polymerized rosin wherein unmodified rosin is modified by hydrogenation, disproportionation, or polymerization; or combinations thereof. Rosin derivative resins are derivatives of the above rosin types, including derivatives of unmodified rosin, derivatives of modified rosin, or combinations thereof. Rosin derivative resins may include: rosin esters, such as unmodified rosin esters—which are esters of unmodified rosin and alcohol, or modified rosin esters—which are esters of modified rosin and alcohol; unsaturated fatty acid modified rosin, wherein the rosin is modified with unsaturated fatty acids; unsaturated fatty acid modified rosin esters, wherein the rosin esters are modified with unsaturated fatty acids; rosin alcohols, wherein the carboxyl groups of rosin or various rosin derivatives (including rosin esters, unsaturated fatty acid modified rosin, and unsaturated fatty acid modified rosin esters) are reduced; metal salts of rosin or various rosin derivatives; or combinations thereof.

[0085] Terpene resins may include polymers of terpenes (e.g., monoterpenes) selected from terpenes such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene; aromatic modified terpene resins; styrene modified terpene resins; hydrogenated terpene resins; and terpene phenol resins. The terpene polymer may be a homopolymer of one terpene or a copolymer of two or more terpenes. Terpene phenol resins refer to polymers comprising terpene residues and phenol residues, wherein terpene phenol resins may include: copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins); homopolymers or copolymers of phenol-modified terpenes (phenol-modified terpene resins); or combinations thereof.

[0086] Hydrocarbon resins may include at least one selected from aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic petroleum resins, aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic-alicyclic petroleum resins, coumarone resins, and coumarone-indene resins. For example, aliphatic petroleum resins may be C5 type petroleum resins, and aromatic petroleum resins may be C9 type petroleum resins.

[0087] Hydrogenated hydrocarbon resins refer to resins in which the hydrocarbon resin is hydrogenated.

[0088] Styrene-based resins may include at least one selected from poly-α-methylstyrene, α-methylstyrene / styrene copolymers, styrene monomer / aliphatic monomer copolymers, styrene monomer / α-methylstyrene / aliphatic monomer copolymers, styrene monomer copolymers, and styrene monomer / aromatic monomer copolymers.

[0089] Phenolic resins can be selected from at least one of terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol resins, and rosin phenol resins. Terpene phenol resins are the same as described above, and hydrogenated terpene phenol resins refer to resins having a structure formed by hydrogenating the aforementioned terpene phenol resins. Rosin phenol resins refer to phenol-modified rosin or rosin derivative resins such as rosin esters, unsaturated fatty acid-modified rosin, and unsaturated fatty acid-modified rosin esters, and, for example, rosin phenol resins can be obtained by adding phenol as an acid catalyst to rosin or rosin derivative resins to perform thermal polymerization.

[0090] Xylene resins may include at least one selected from xylene resins, alkylphenol xylene resins, linear phenolic resins, methyl phenolic xylene resins, polyol-modified xylene resins, and ethylene oxide-modified xylene resins.

[0091] Based on the total weight of the adhesive layer 12, the tackifier may be included in an amount greater than or equal to 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45% by weight, and may also be included in an amount less than or equal to 50%, 45%, 35%, 30%, 25%, 20%, 15%, or 10% by weight. These ranges can be combined without limitation. For example, based on the total weight of the adhesive layer 12, the tackifier may be included in an amount of 5% to 50%, 5% to 30%, 5% to 20%, or 5% to 15% by weight. Under the above conditions, since the adhesive layer can have excellent initial adhesion properties, the adhesion force of the adhesive layer can be ensured to be above a certain level, and the excellent adhesion force can be maintained in a wide range of temperatures from high temperature to room temperature, thus preventing the separation of the adhesive film.

[0092] The thermosetting resin and tackifier can be included in the adhesive layer 12 in a weight ratio of 1:99 to 99:1, 30:70 to 99:1, 50:50 to 95:5, 60:40 to 95:5, or 70:30 to 90:10. While meeting the above weight ratios, adhesion and heat resistance can be appropriately adjusted to ensure excellent adhesion over a wide temperature range from high temperatures to room temperature.

[0093] The adhesive layer 12 can have a thickness of 10 μm to 100 μm, 12 μm to 80 μm, 20 μm to 50 μm, or 30 μm to 50 μm. When these ranges are met, the heat resistance of the adhesive film can be improved because the adhesion to polyester resin substrates and stainless steel substrates can be further improved while the adhesive layer has sufficient strength.

[0094] pouch-type secondary batteries

[0095] A pouch-type secondary battery according to an embodiment of the present invention includes: an electrode assembly including a positive electrode, a negative electrode, and a separator; a pouch-type case including a receiving portion for receiving the electrode assembly, and a platform portion and a sealing portion formed along the periphery of the receiving portion; an electrode tab protruding from each of the positive and negative electrodes of the electrode assembly; an electrode lead connected to the electrode tab and protruding outwardly via the platform portion; and an adhesive film according to claim 1, the adhesive film being configured to surround a cross-section exposed at the end of the sealing portion.

[0096] Figure 2 This is an exploded assembly diagram of the pouch-type secondary battery 100 according to the present invention, and Figure 3 This is a cross-sectional view of a sealed pouch-type secondary battery 100.

[0097] In the following text, reference will be made to Figure 2 and Figure 3 The various configurations of the pouch-type secondary battery according to the present invention will be described in more detail.

[0098] (1) Electrode assembly

[0099] The electrode assembly includes a positive electrode, a negative electrode, and a separator.

[0100] According to an embodiment of the present invention, the electrode assembly 160 can be inserted into the pouch box 110 and can be sealed by the pouch box 110 after electrolyte injection.

[0101] Electrode assembly 160 can be formed by sequentially stacking a positive electrode, a spacer, and a negative electrode. Specifically, electrode assembly 160 may include two types of electrodes, such as a positive electrode and a negative electrode, and a spacer disposed between the electrodes to insulate them from each other.

[0102] The positive and negative electrodes can be structures in which an active material slurry is applied, respectively, to an electrode current collector in the form of a metal foil or mesh, including aluminum and copper. The slurry is typically formed by stirring granular active material, auxiliary conductors, binders, and conductive agents with a solvent added. The solvent can be removed in subsequent processes.

[0103] A slurry containing electrode active materials, binders, and / or conductive agents is applied to a positive current collector and a negative current collector to prepare positive and negative electrodes. The electrode assembly 160 can be prepared in a predetermined shape by stacking the positive and negative electrodes on two sides of a separator. The type of electrode assembly 160 may include, but is not limited to, stacked, wound, and stacked and folded types.

[0104] (2) Bag-type box

[0105] The bag-shaped box includes: a receiving portion for accommodating the electrode assembly, and a platform portion and a sealing portion formed along the periphery of the receiving portion.

[0106] According to an embodiment of the present invention, the pouch box 110 may internally house the electrode assembly 160. The pouch box 110 may be fabricated by forming a pouch film laminate. In this case, the pouch film laminate may include a base material layer, a gas barrier layer, and a sealant layer. In the pouch film laminate, the base material layer, the gas barrier layer, and the sealant layer may be laminated sequentially.

[0107] The base material layer forms the outermost layer of the pouch film laminate to protect the secondary battery from external friction and impact. The base material layer is formed of a polymer, which allows it to electrically insulate the electrode assembly from external sources.

[0108] The base material layer may be formed of at least one material selected from polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aromatic polyamide, nylon, polyester, poly(p-benzodioxazole), polyarylate, polytetrafluoroethylene, and glass fiber. Preferably, the base material layer may be formed of polyethylene terephthalate (PET), nylon, or combinations thereof, which have abrasion resistance and heat resistance.

[0109] The base material layer can be a single-layer structure formed of any material. Alternatively, the base material layer can be a composite layer structure formed by laminating two or more materials separately.

[0110] The thickness of the base material layer can be from 5 μm to 50 μm, particularly from 7 μm to 40 μm, and even more particularly from 25 μm to 38 μm. When the thickness of the base material layer meets the above ranges, the energy density of the secondary battery can be excellent relative to its volume due to excellent external insulation and a thin overall bag.

[0111] A gas barrier layer is laminated between the base material layer and the sealant layer to ensure the mechanical strength of the bag, prevent gas or moisture from flowing in and out of the secondary battery, and prevent electrolyte from leaking from the inside of the bag box.

[0112] The gas barrier layer can be formed of a metal, and specifically, it can be formed of an aluminum alloy thin film. When the gas barrier layer is formed using an aluminum alloy thin film, it is lightweight while ensuring mechanical strength above a predetermined level, compensating for the electrochemical performance of the electrode assembly and electrolyte, and ensuring heat dissipation. The aluminum alloy thin film may include metallic elements other than aluminum (Al), such as at least one selected from iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0113] The thickness of the gas barrier layer can be from 40 μm to 100 μm, particularly from 50 μm to 90 μm, and even more particularly from 55 μm to 85 μm. When the thickness of the gas barrier layer meets the above range, the gas barrier performance and formability are excellent when forming the cup-shaped portion.

[0114] The sealant layer is used to completely seal the interior of a pouch containing electrode assemblies by thermally bonding them together at the sealing portions. For this purpose, the sealant layer can be formed of a material with excellent thermal bonding strength.

[0115] The sealant layer can be formed of a material with insulating, corrosion-resistant, and sealing properties. Specifically, since the sealant layer is in direct contact with the electrode components and / or electrolyte inside the pouch, it can be formed of a material with insulating and corrosion-resistant properties. Furthermore, because the sealant layer completely seals the interior of the pouch to prevent material movement between the inside and outside, it can be formed of a material with high sealing properties (e.g., excellent thermal adhesion strength). To ensure these insulating, corrosion-resistant, and sealing properties, the sealant layer can be formed of a polymer material.

[0116] The sealant layer may be formed from at least one material selected from polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aromatic polyamide, nylon, polyester, poly(p-benzodioxazole), polyarylate, polytetrafluoroethylene, and glass fiber, and may preferably be formed from polyolefin resins such as polypropylene (PP) and / or polyethylene (PE). In this case, polypropylene may include cast polypropylene (CPP), acid-modified polypropylene (PPa), polypropylene-ethylene copolymer, and / or polypropylene-butene-ethylene terpolymer.

[0117] The thickness of the sealant layer can be from 30 μm to 130 μm, particularly from 50 μm to 120 μm, and even more particularly from 70 μm to 100 μm. When the thickness of the sealant layer meets the above range, it has the effect of ensuring the sealing strength of the sealed part while ensuring the formability of the bag film laminate.

[0118] The bag-shaped box 110 can be prepared by pulling and stretching the bag film laminate using a punch or the like. Therefore, the bag-shaped box 110 may include a cup-shaped portion 122 and a receiving portion 124. The receiving portion 124 is a place for receiving electrode assemblies, wherein the receiving portion 124 may refer to a receiving space formed in the cup-shaped portion 122 as a recess when the cup-shaped portion 122 is formed.

[0119] According to embodiments of the present invention, such as Figure 1 As illustrated, the pouch-type case 110 may include a first case 120 and a second case 130. The first case 120 includes a receiving portion 124 capable of accommodating the electrode assembly 160, and the second case 130 can cover the receiving portion 124 from the top, such that the electrode assembly 160 does not detach from the outside of the battery case 110. Figure 1 As illustrated, the first box 120 and the second box 130 can be prepared by connecting one side of them to each other, but the invention is not limited thereto. The first box 120 and the second box 130 can be prepared in various ways, for example, the first box 120 and the second box 130 can be separated from each other and prepared separately.

[0120] According to another embodiment of the invention, when the cup-shaped portions are formed on the bag film laminate, two symmetrical cup-shaped portions 122 and 132 can be pulled adjacent to each other on a bag film laminate. In this case, as Figure 1As illustrated, cup-shaped portions 122 and 132 can be formed in the first box 120 and the second box 130, respectively. After the electrode assembly 160 is accommodated in the receiving portion 124 provided in the cup-shaped portion 122 of the first box 120, the bridging portion 140 formed between the two cup-shaped portions 122 and 132 can be folded so that the two cup-shaped portions 122 and 132 face each other. In this case, the cup-shaped portion 132 of the second box 130 can accommodate the electrode assembly 160 from above. Therefore, since the two cup-shaped portions 122 and 132 accommodate one electrode assembly 160, an electrode assembly 160 with a greater thickness than when there is only one cup-shaped portion 122 can be accommodated. Furthermore, since one edge of the secondary battery 100 is formed by folding the pouch-shaped box 110, the number of edges to be sealed can be reduced when a sealing process is performed later. Therefore, the processing speed of the pouch-shaped secondary battery 100 can be improved, and the number of sealing processes can be reduced.

[0121] The pouch-type box 110 can be sealed while containing the electrode assembly 160, exposing a portion of the electrode lead 180, i.e., the terminal portion, as described later. Specifically, when the electrode lead 180 is connected to the electrode tab 170 of the electrode assembly 160 and a lead film 190 is formed in a portion of the electrode lead 180, the electrode assembly 160 is contained in a receiving portion 124 disposed in the cup-shaped portion 122 of the first box 120, and the second box 130 can cover the receiving portion 124 from the top. Subsequently, electrolyte is injected into the receiving portion 124, and a portion of the peripheral portion 150 formed on the edge along the periphery of the first box 120 and the second box 130 can be sealed to form a sealing portion 300 and a platform portion 400.

[0122] Therefore, the bag-shaped box includes a receiving portion for accommodating the electrode assembly, a platform portion formed along the periphery of the receiving portion, and a sealing portion.

[0123] The sealing portion 300 refers to the area where the electrode leads of the sealed peripheral portion 150 do not protrude from it.

[0124] The platform portion 400 refers to the area where the electrode leads of the sealed peripheral portion 150 protrude from, and the electrode leads protrude to the outside via the platform portion.

[0125] The sealing portion 300 and the platform portion 400 can be used to seal the receiving portion 124. Specifically, the sealing portion 300 and the platform portion 400 can seal the receiving portion 124 when formed on the peripheral portion 150, which is formed on the edge along the periphery of the receiving portion 124.

[0126] The sealing temperature of the sealing portion 300 and the platform portion 400 can be within the range of 180°C to 250°C, 200°C to 250°C, or 210°C to 240°C. When the sealing temperature meets these ranges, the bag box 110 can ensure sufficient sealing strength through heat bonding.

[0127] The sealing portion 300 can be folded such that its end 302 faces the receiving portion 124, and specifically, the width of the sealing portion 300 can be folded by 30% to 70%, 35% to 65%, or 40% to 60%. In this case, the width of the sealing portion 300 can refer to the length from the boundary between the receiving portion 124 and the sealing portion 300 to the end 302 of the sealing portion. In this case, the energy density of the lithium secondary battery can be increased and the venting pressure can be increased.

[0128] The sealing portion 300 can be folded 180° (with an error range of ±10%) so that the end 302 of the sealing portion faces the receiving portion 124. In this case, since the end 302 of the sealing portion is protected by the adhesive film, the metal barrier layer is not exposed, thus providing the advantage of more effectively ensuring insulation performance and minimizing damage to the sealing portion.

[0129] (3) Electrode contacts

[0130] Electrode contacts 170 protrude from each of the positive and negative electrodes of the electrode assembly 160.

[0131] Specifically, electrode tab 170 is connected to each of the positive and negative electrodes of electrode assembly 160 and protrudes from the electrode assembly 160 to the outside, such that electrode tab 170 can be a path through which electrons can move between the inside and outside of electrode assembly 160. The electrode current collector included in electrode assembly 160 may include a portion to which electrode active material is applied and an end portion to which no electrode active material is applied, i.e., an uncoated portion. Electrode tab 170 can be formed by cutting the uncoated portion, or by connecting individual conductive members to the uncoated portion by means of ultrasonic welding or the like. Figure 1 As illustrated, the electrode tabs 170 may protrude in different directions along the electrode assembly 160, but are not limited thereto, and may be formed to protrude in various directions. For example, the electrode tabs 170 may protrude side by side in the same direction from one side of the electrode assembly 160.

[0132] (4) Electrode leads

[0133] The electrode leads are connected to the electrode contacts, protruding to the outside of the pouch box, and specifically, protruding to the outside via the platform portion of the pouch box.

[0134] Specifically, the electrode lead 180 can supply power to the outside of the pouch-type secondary battery 100. The electrode lead 180 can be connected to the electrode tab 170 of the electrode assembly 160 by spot welding or the like.

[0135] Electrode lead 180 is connected to electrode assembly 160 and can protrude to the outside of pouch 110 via platform portion 400. Specifically, one end of electrode lead 180 is connected to electrode assembly 160, particularly electrode tab 170, and the other end of electrode lead 180 can protrude to the outside of pouch 110 via platform portion 400.

[0136] Electrode leads 180 may include a positive lead 182 and a negative lead 184. One end of the positive lead 182 is connected to the positive terminal 172 and extends in the protruding direction of the positive terminal 172. One end of the negative lead 184 is connected to the negative terminal 174 and extends in the protruding direction of the negative terminal 174. The other end of both the positive lead 182 and the negative lead 184 may protrude to the outside of the battery case 110. Therefore, power generated inside the electrode assembly 160 can be supplied to the outside. Furthermore, since the positive terminal 172 and the negative terminal 174 are formed to protrude in different directions, the positive lead 182 and the negative lead 184 may also extend in different directions. The materials of the positive lead 182 and the negative lead 184 may be different from each other. In other words, the positive electrode lead 182 can be formed of the same aluminum (Al) material as the positive current collector, and the negative electrode lead 184 can be formed of the same copper (Cu) material as the negative current collector or nickel (Ni) coated copper material. Since the portion of the electrode lead 180 protruding to the outside of the pouch 110 becomes a terminal portion, the electrode lead 180 can be electrically connected to an external terminal.

[0137] A film layer 200, comprising at least one selected from chromium (Cr), nickel (Ni), alumina (Al₂O₃), zirconium (Zr)-based anhydrous oxide salts, and titanium (Ti)-based anhydrous oxide salts, can be formed on a surface of the electrode lead 180 that is in direct contact with the lead film 190 and / or the gas emission portion (not shown). In this case, corrosion resistance to the electrolyte solution and adhesion to the lead film 190 and / or the gas emission portion can be ensured.

[0138] Electrode lead 180 may include lead film 190.

[0139] The lead film 190 prevents the electricity generated from the electrode assembly 160 from flowing through the electrode leads 180 to the pouch 110 and maintains the seal of the pouch 110. For this purpose, the lead film 190 can be formed of a non-conductive insulator that does not conduct electricity well. Typically, relatively thin insulating tapes or films that are easy to attach to the electrode leads 180 are widely used as the lead film 190, but the invention is not limited to this, and any component capable of insulating the electrode leads 180 can be used.

[0140] The lead film 190 can be configured to surround the outer peripheral surface of the electrode lead 180. Specifically, at least a portion of the electrode lead 180 can be surrounded by the lead film 190. In this case, the lead film 190 can be disposed between the electrode lead 180 and the pouch cassette 110. The lead film 190 can be specifically located at the sealing portion 300 where the first box 120 and the second box 130 of the pouch cassette 110 are thermally fused, and can adhere the electrode lead 180 to the pouch cassette 110.

[0141] (5) Adhesive film

[0142] The structure and composition of the adhesive film 10 are the same as described above, so a detailed description is omitted.

[0143] The adhesive film 10 according to the invention is configured to surround the exposed section at the end 302 of the sealing portion 300.

[0144] Specifically, the adhesive film 10 can be positioned to cover both surfaces of the sealing portion 300, while also being positioned to surround the exposed section at the end 302 of the sealing portion 300—where the electrode lead 180 does not protrude. Alternatively, the adhesive film 10 can be positioned to cover both surfaces of the sealing portion 300 with the same area, while also being positioned to surround the exposed section at the end 302 of the sealing portion 300—where the electrode lead 180 does not protrude. In this case, the gas barrier layer included in the pouch film laminate can be prevented from being exposed at the end of the sealing portion, and thus, the effect of preventing battery short circuits and maintaining the insulation performance of the pouch box can be achieved.

[0145] In this configuration, where the adhesive film 10 is positioned to cover both surfaces of the sealing portion 300, the adhesive film 10 can cover 20% to 80%, 30% to 70%, or 40% to 60% of the surface area of ​​the sealing portion 300. Furthermore, the adhesive film 10 can cover at least 50%, 60%, 70%, or 80% of the periphery of the sealing portion 300.

[0146] Figure 4 This is a cross-sectional view of a pouch-shaped secondary battery 100 with the sealed portion 300 folded.

[0147] Reference Figure 4 With the adhesive film 10 positioned to surround the exposed section of the end 302 of the sealing portion 300—where the electrode lead 180 does not protrude—the sealing portion 300 can be folded such that the end 302 of the sealing portion faces the receiving portion 124. Specifically, the sealing portion 300 can be folded 180° such that the end 302 of the sealing portion faces the receiving portion 124. When the sealing portion 300 is folded, the adhesive film 10 can be positioned on the folded sealing portion.

[0148] After folding the sealing portion 300, the folded sealing portion 300 can be pressed at a high temperature. Therefore, the energy density of the lithium secondary battery can be improved by fixing the sealing portion in a folded state. Furthermore, during pressing, the adhesive film disposed on the outer surface of the sealing portion is also pressed at a high temperature. Wherein, when the adhesive film used in conventional single-sided or double-sided folding is pressed at a high temperature, there is a problem of adhesive film separation or melting and leakage of adhesive layer components. In contrast, the lithium secondary battery according to the present invention solves the problems of adhesive film separation and leakage of adhesive layer components during the wing-folding process, which substantially requires a high-temperature pressing process, by disposing of an adhesive film with a certain level or higher adhesion at a high temperature on the exposed cross-section at the end of the sealing portion.

[0149] Specifically, the folded sealing portion 300 can be pressed using a hot press. In this case, the folded sealing portion 300 can be pressed using a hot press at pressures of 0.01 MPa to 1 MPa, 0.05 MPa to 0.7 MPa, or 0.1 MPa to 0.5 MPa. In this case, by fixing the sealing portion in the folded state, the energy density of the battery is increased, and separation of the adhesive film at the end of the sealing portion due to overheating of the folded sealing portion is prevented. Therefore, exposure of the end of the folded sealing portion is prevented, and thus, the insulation performance and safety of the battery case are maintained because the gas barrier layer of the bag film laminate is prevented from being exposed to the outside.

[0150] (6) Electrolytes

[0151] The pouch-type secondary battery 100 according to the present invention may further include an electrolyte (not shown) injected into the pouch-type case 110.

[0152] As the electrolyte, various electrolytes suitable for lithium secondary batteries can be used, such as organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes, and their types are not particularly limited.

[0153] Specifically, electrolytes may include organic solvents and lithium salts.

[0154] Any organic solvent can be used without particular restriction, as long as it serves as a medium through which the ions involved in the electrochemical reactions of the battery can move. Specifically, the following can be used as organic solvents: ester solvents, such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents, such as dibutyl ether or tetrahydrofuran; ketone solvents, such as cyclohexanone; aromatic hydrocarbon solvents, such as benzene and fluorobenzene; or carbonate solvents, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents, such as ethanol and isopropanol; nitriles, such as R-CN (where R is a linear, branched, or cyclic C2-C20 hydrocarbon group, and may include double-bonded aromatic rings or ether bonds); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane; or sulfolane. Among these solvents, carbonate solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant—which can improve the charge / discharge performance of the battery—with low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are even more preferred.

[0155] Lithium salts can be used without particular limitation, as long as they are compounds capable of providing lithium ions for use in lithium secondary batteries. Specifically, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2 can be used as lithium salts. The lithium salt can be used in a concentration range of 0.1 M to 5.0 M, preferably 0.1 M to 3.0 M. If the concentration of the lithium salt is within this range, excellent electrolyte performance can be obtained because the electrolyte can have suitable conductivity and viscosity, and lithium ions can move efficiently.

[0156] To improve battery life characteristics, suppress battery capacity reduction, and improve battery discharge capacity, additives may be included in the electrolyte in addition to the electrolyte components mentioned above. For example, as additives, halogenated alkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxetane, N,N-substituted imidazolides, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride may be used alone or in mixtures thereof, but the invention is not limited thereto. Based on the total weight of the electrolyte, the additives may be included in an amount of 0.1% to 10% by weight, preferably 0.1% to 5% by weight.

[0157] Examples and Comparison Examples

[0158] Example 1

[0159] The composition for forming the adhesive layer is prepared by mixing polydimethylsiloxane (PDMS) with vinyl ends as a thermosetting resin with a dimethylsiloxane-methylhydrosiloxane copolymer as a curing agent at a weight ratio of 98:2.

[0160] A polyethylene terephthalate (PET) film was prepared as the outer insulating layer, and an adhesive film was prepared by coating one surface of the PET film with the above-prepared composition for forming the adhesive layer, and then drying at 140°C for 3 minutes to form the adhesive layer. In the prepared adhesive film, the thickness of the outer insulating layer was 25 μm, and the thickness of the adhesive layer was 40 μm.

[0161] Example 2

[0162] The adhesive film was prepared in the same manner as in Example 1, except that the thickness of the adhesive layer in the prepared adhesive film was 20 μm.

[0163] Example 3

[0164] The adhesive film was prepared in the same manner as in Example 1, except that a 25 μm thick polyimide (PI) film was used as the outer insulating layer.

[0165] Example 4

[0166] The adhesive film was prepared in the same manner as in Example 1, except that an epoxy resin with OH groups was used instead of polydimethylsiloxane as the thermosetting resin, and an imidazole curing agent (C11Z-A) was used as the curing agent.

[0167] Comparison Example 1

[0168] The composition for forming the adhesive layer is prepared by mixing an acrylic copolymer comprising acrylic acid (AA), butyl acrylate (BA), and ethylhexyl acrylate (EHA) as an acrylic resin with a rosin ester tackifier in a weight ratio of 90:10.

[0169] A polyethylene terephthalate (PET) film was prepared as the outer insulating layer, and an adhesive film was prepared by coating one surface of the PET film with the above-prepared composition for forming the adhesive layer, and then drying at 140°C for 3 minutes to form the adhesive layer. In the prepared adhesive film, the thickness of the outer insulating layer was 25 μm, and the thickness of the adhesive layer was 40 μm.

[0170] Comparison Example 2

[0171] The adhesive film was prepared in the same manner as in Comparative Example 1, except that the thickness of the outer insulating layer in the prepared adhesive film was 40 μm and the thickness of the adhesive layer was 7 μm.

[0172] Comparison Example 3

[0173] The adhesive film was prepared in the same manner as Comparative Example 1, except that a polyimide (PI) film with a thickness of 25 μm was used as the outer insulating layer.

[0174] Comparison Example 4

[0175] The adhesive film was prepared in the same manner as in Example 1, except that the thermosetting resin and the curing agent were mixed in a weight ratio of 99.5:0.5.

[0176] Experimental Example 1: Adhesion Force Measurement Test

[0177] 1) Measurement of adhesion force on stainless steel substrate

[0178] Each adhesive film prepared in Examples 1 to 4 and Comparative Examples 1 to 4 was cut to a size of 25 mm × 150 mm. The cut adhesive film, with the surface opposite to the adhesive layer pressed, was pressed onto a SUS304 substrate serving as a stainless steel substrate using a 2 kg roller. The adhesive film was then peeled at 140°C at a peel speed of 300 mm / min and a peel angle of 180°, and the adhesion force under these conditions was measured using ASTM D 3330. The measurement results are shown in Table 1 below.

[0179] 2) Measurement of adhesion to polyester resin substrates

[0180] Each adhesive film prepared in Examples 1 to 4 and Comparative Examples 1 to 4 was cut to a size of 25 mm × 150 mm. The cut adhesive film, with the surface opposite to the adhesive layer pressed, was pressed onto a polyethylene terephthalate (PET) substrate, which served as a polyester resin substrate, using a 2 kg roller. The adhesive film was then peeled at 140°C, a peel speed of 300 mm / min, and a peel angle of 180°, and the adhesion force under these conditions was measured using ASTM D 3330. The measurement results are shown in Table 1 below.

[0181] [Table 1]

[0182] Experimental Example 2: Measurement of Storage Modulus and Loss Modulus

[0183] The adhesive layers included in the adhesive films prepared by Examples 1 to 4 and Comparative Examples 1 to 4 were laminated on parallel plates with a diameter of 8 mm to a thickness of 800 μm to 1000 μm, and then cut by punching with a punch with a diameter of 8 mm. Subsequently, the storage modulus (G') and loss modulus (G”) of the adhesive films were measured using their respective DHR-20 rotational rheometers (manufacturer: TA Instruments). All measurements were performed at a frequency of 1 Hz and 140°C under oscillating frequency sweep mode, with an axial force of 100 gf, a strain of 5%, and a frequency range of 0.1 Hz to 100 Hz.

[0184] The measurement results are shown in Table 2 below.

[0185] [Table 2]

[0186] Experimental Example 3: Adhesive Membrane Separation Test

[0187] The lithium secondary battery was fabricated using the adhesive films prepared in Examples 1 to 4 and Comparative Examples 1 to 4. Specifically, after accommodating the electrode assembly in the receiving portion of the pouch-type battery case, the upper portion of the receiving portion was covered, and the peripheral portion formed along the periphery of the receiving portion was sealed. Subsequently, after each adhesive film was positioned such that the end of the sealed portion—where the electrode leads do not protrude—was adhered to each other with the adhesive layer of each adhesive film prepared in Examples 1 to 4 and Comparative Examples 1 to 4 and in a manner that surrounds the end of the sealed portion, the sealed portion was folded 180° such that the end of the sealed portion faced the receiving portion to fabricate each lithium secondary battery.

[0188] In the lithium secondary batteries prepared above, the sealed portion—which was in a folded state with the adhesive films prepared in Examples 1 to 4 and Comparative Examples 1 to 4 adhered to it—was pressed at a temperature of 140°C. In this case, it was visually confirmed whether each adhesive film prepared in Examples 1 to 4 and Comparative Examples 1 to 4 separated from the outer surface of the pouch-type battery case of each lithium secondary battery, and the results are shown in Table 3 below.

[0189] - O: The adhesive film separates from the outer surface of the pouch-shaped battery box.

[0190] - X: The adhesive film has not separated from the outer surface of the pouch-type battery box.

[0191] [Table 3]

[0192] Referring to Table 3, it can be confirmed that the adhesive films prepared in Examples 1 to 4 do not separate when pressed at 140°C, but the adhesive films prepared in Comparative Examples 1 to 4 separate when pressed at 140°C.

[0193] (Description of reference numerals in the attached figures)

[0194] 10: Adhesive film

[0195] 11: Outer insulation layer

[0196] 12: Adhesive layer

[0197] 100: Pouch-type secondary battery

[0198] 110: Bag-type box

[0199] 120: First box

[0200] 122: Cup-shaped part

[0201] 124: Containment section

[0202] 130: Second box

[0203] 132: Cup-shaped part

[0204] 140: Bridging section

[0205] 150: Peripheral Section

[0206] 160: Electrode assembly

[0207] 170: Electrode contacts

[0208] 172: Positive electrode connector

[0209] 174: Negative electrode connector

[0210] 180: Electrode lead

[0211] 182: Positive lead

[0212] 184: Negative lead

[0213] 190: Lead film

[0214] 200: film layer

[0215] 300: Sealing part

[0216] 302: End of the sealing part

[0217] 400: Platform section.

Claims

1. An adhesive film, comprising: Outer insulation layer; as well as An adhesive layer is disposed on one surface of the outer insulating layer. The adhesive layer comprises a thermosetting resin, and The adhesive film satisfies at least one of the following: an adhesion force of ≥100 gf / 25 mm to a stainless steel substrate and an adhesion force of ≥200 gf / 25 mm to a polyester resin substrate. The adhesion force is the force exerted when the adhesive film is peeled off at 140°C, at a peeling speed of 300 mm / min and a peeling angle of 180° after pressing the surface of the adhesive layer opposite to the surface in contact with the outer insulating layer onto the stainless steel substrate or the polyester resin substrate using a 2 kg roller.

2. The adhesive film according to claim 1, wherein, The outer insulation layer comprises at least one selected from polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyimide, cast polypropylene, high-density polyethylene, and low-density polyethylene.

3. The adhesive film according to claim 1, wherein, The thermosetting resin is a silicone resin, an epoxy resin, or a combination of silicone resin and epoxy resin.

4. The adhesive film according to claim 1, wherein, The adhesive layer includes a curing agent.

5. The adhesive film according to claim 4, wherein, The thermosetting resin is a silicone resin, and The curing agent includes silane groups (Si-H groups).

6. The adhesive film according to claim 4, wherein, The thermosetting resin is epoxy resin, and The curing agent is an amine-based curing agent.

7. The adhesive film according to claim 1, wherein, The adhesive layer includes a tackifier.

8. The adhesive film according to claim 7, wherein, The tackifier includes at least one selected from rosin resins, terpene resins, hydrocarbon resins, hydrogenated hydrocarbon resins, styrene resins, phenolic resins, and xylene resins.

9. The adhesive film according to claim 1, wherein, The stainless steel substrate is a SUS304 substrate.

10. The adhesive film according to claim 1, wherein, The polyester resin substrate is a polyethylene terephthalate (PET) substrate.

11. The adhesive film according to claim 1, wherein, The thermosetting resin is included in an amount ranging from 10% to 99% by weight, based on the total weight of the adhesive layer.

12. The adhesive film according to claim 1, wherein, The adhesion of the adhesive film to the stainless steel substrate and the polyester resin substrate is less than or equal to 500 gf / 25 mm.

13. The adhesive film according to claim 1, wherein, The storage modulus (G') of the adhesive layer at 140°C is 1×10⁻⁶. 4 Pa to 1×10 6 Within the range of Pa.

14. The adhesive film according to claim 1, wherein, The loss modulus (G) of the adhesive layer at 140°C is 2 × 10⁻⁶. 3 Pa to 1×10 5 Within the range of Pa.

15. The adhesive film according to claim 1, wherein, The tanδ (G” / G’) of the adhesive layer at 140°C is in the range of 0.01 to 0.

45.

16. The adhesive film according to claim 1, wherein, The adhesive film has a thickness of 30 µm to 150 µm.

17. A pouch-type secondary battery, comprising: The electrode assembly includes a positive electrode, a negative electrode, and a separator. A bag-shaped box, the bag-shaped box including a receiving portion for receiving the electrode assembly, and a platform portion and a sealing portion formed along the periphery of the receiving portion; Electrode tabs protrude from each of the positive and negative electrodes of the electrode assembly; Electrode leads, which are connected to the electrode tabs and protrude outwards via the platform portion; as well as According to claim 1, the adhesive film is configured to surround a cross-section exposed at the end of the sealing portion.

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